Chain saws are normally employed in logging operations for the harvesting of timber. Chain saws are employed to fell trees and to reduce them to logs of manageable size. Chain saws may be powered by self-contained gasoline engines and are employed in situations where the depth of cut is more than a few inches and a wide kerf is desirable or acceptable. Though usually employed in logging operation, chain saws are employed whenever large timbers must be cut or shaped, as in the construction of log and timber-frame houses. Certain specialized, low volume, portable lumber mills employ chain saws for the production of dimension timber from logs.
Unlike a conventional saw blade where the cutting teeth have a single cutting edge and are integral with the peripheral edge of the saw disc in a circular saw, or the linear edge of a steel band in a band saw, the cutting teeth on a chain saw are fashioned from portions of links in a chain. Because the chain must cut a wide kerf to allow passage of the chain and the supporting chain saw bar, the teeth on chain saws normally have two cutting surfaces; one perpendicular to the saw kerf, and the other parallel to the saw kerf. The two cutting surfaces normally join at right angles in a chisel-bit-type cutter tooth or a single curved surface may be used which extends into the two planes perpendicular and parallel to the saw kerf.
The specialized shape of the cutting teeth on a chain saw and their location on links in a chain makes them unsuitable for sharpening on a conventional saw sharpening tool. Chain saws often require frequent sharpening. Chain saws generally do not incorporate tungsten carbide inserts which have lessened the requirement of sharpening conventional circular saws. Chain saws are often used in situations where the blade may come in contact with dirt or materials having embedded grit contained therein. It is not unusual that a chain saw employed in a logging operation may require daily sharpening in order to maintain the efficiency of the log harvesting process.
Chain saws may be sharpened with a round or triangular file which is drawn along the cutting surfaces of each tooth. This can be a tedious and time-consuming process, and numerous saw sharpeners have been developed to reduce the labor and improve the accuracy with which chain saws chains are sharpened.
One known type of chain saw sharpener employs a rotating cylindrical stone sized so that the cylindrical surface may form the cutting edges on the chain saw tooth. However, because of the small diameter of these cylindrical teeth sharpeners, they are prone to rapid wear which can result in uneven shaping of the cutting surfaces.
Other known chain saw chain sharpening machines employ grinding wheels which are shaped to form the proper cutting surfaces on the chain saw chain teeth. However, the abrasive wheels are formed of a brittle material and a substantial wheel section must be co-extensive with the shaping surface of the wheel in order to support the shaping surfaces in contact with the chain saw teeth.
The cutting surfaces of a chain saw tooth are proceeded on the tooth by a depth gauge, which controls the depth of cut. This depth gauge limits the accessibility of the cutting edges and, therefore, imposes limitations on the ability of a grinding disc to access the cutting surfaces of the tooth to form an optimal cutting surface thereon.
What is needed is a chain saw sharpening tool employing the advantages of a grinding wheel, but able to gain better access to the cutting surfaces through the gap formed between the depth gauge and the cutting surfaces.